Swedish Bone Drug Study Confirms Rare Thigh Fracture Risk

Bisphosphonates, a class of drugs used to treat osteoporosis that includes Aclasta, Actonel, Aredia, Bondronat, Boniva, Didronel, Fosamax, Fosavance, Reclast, Skelid, and Zometa, do increase the risk of certain rare thigh fractures, according to a new study out of Sweden. Like previous research, the study found the bisphosphonate thigh fracture risk was highest among women who were taking them the longest.

The study, published in the May 4 issue of the New England Journal of Medicine, looked at 12,777 women aged 55 and older who suffered a fracture of the thigh bone in 2008. X-ray evaluation revealed that 59 of those women had 59 an atypical femoral (thigh bone) fractures. Seventy-eight percent of those with the atypical femoral fractures were on bisphosphonates, while only 10 percent who suffered other types of thigh fractures were taking the drugs.

In another portion of the study, the researchers looked at 1.5 million women in the National Swedish Patient Registry who were 55 or older in 2008. The 83,000 who used bisphosphonates were categorized according to length of use – one year, one to 1.9 years, or two years or more. Among women taking the drugs for one or two years, the risk of an atypical fracture was increased by factors of 18.4 and 17.0, respectively, compared women not using bisphosphonates. Among women who used the drugs for longer than two years, the relative risk rose to 67.0. The study authors concluded that each 100 daily doses of bisphosphonates increased the risk by 30 percent.

They also found that when women stopped taking bisphosphonates, the risk of atypical thigh fractures dipped. Those off the drugs for a year had a relative risk for atypical femoral fractures of 3.5 or less, with a similar reduction seen among those who had stopped treatment for two years or more. This led the researchers to conclude that each year after the last dose reduced the atypical thigh fracture risk by 70 percent.

Melvin Rosenwasser, MD, professor of orthopaedic surgery at the Columbia University College of Physicians and Surgeons, New York told WebMD that the study’s findings indicate that women taking bisphosphonates should be periodically reevaluated.

“If you have been taking the drug for five years, you should be tested to see if you still need to take anything,” he said.

This is not the first time a study has confirmed a link between these types of thigh fractures and bisphosphonates. Last year, a study conducted by the American Society of Bone and Mineral Research Subtrochanteric Femoral Fracture Task Force examined more than 300 cases involving women who had suffered subtrochanteric (just below the hip joint) or diaphyseal femur (breaks in the long part of the thigh bone) fractures. The study found that 94 percent of the patients with such fractures had taken bisphosphonates for osteoporosis, and most had been on the drugs for five years or more.

That study prompted the U.S. Food & Drug Administration (FDA) to ask the manufacturers of bisphosphonates to add information to the â€œWarnings and Precautionsâ€ section of the drugs labelsâ€™ describing the risk of atypical thigh fractures.